Conservation agriculture (CA), based on principles of conservation tillage (CT) and crop rotations, has been adopted as a solution to global climate change. However, interactions between these principles and their cumulative effects on soil functions and crop productivity are not yet fully understood. Herein, a 4-year filed experiment was conducted to assess the impact of CA on soil ecosystem multifunctionality (EMF) in the North China Plain (NCP). The results showed that CA improved EMF by up to 532 % compared to traditional agriculture (rotary tillage under wheat and maize rotation system). This enhancement is mainly driven by a 12.3 % increase in soil organic carbon (SOC) storage, an 8.3 % reduction in soil carbon to nitrogen ratio (C: N), a 68.3 % boost in soil enzyme activities index (SEI), and a 59.7 % increase in available phosphorus (AP) under legumebased crop rotations (LBCR) compared to maize-wheat-maize-wheat (MWMW). The principle of CT improved soil physical structure, enhancing soil aggregate stability by up to 38.1 % compared to rotary tillage (RT). Although, the benefits of CT on crop yield were not always observed, positive interactions on crop yield occurred under LBCR combined with CT. For instance, the soybean-wheat-soybean-wheat (SWSW) rotation produced 40.8 % higher yields than the MWMW rotation under CT. Overall, benefits of CT in improving soil structure, along with the increased diversity crop residues, adjustments in soil nutrient stoichiometric ratios, and enhanced soil enzyme activity under LBCR, led to improved SOC sequestration, crop yield and EMF under CA. The positive interactions between the principles of CA demonstrate its ability to enhance ecosystem multifunctionality. As a result, the combination of CT and LBCR within CA is recommended to sustain the productivity in NCP and other regions with similar conditions.

Tailoring straw return strategies to specific regional conditions optimize soil health, crop yield, and carbon emission reduction. This study investigated yield-driven, spatial-scale, and long-term strategies for straw return of maize, rice, and wheat cultivation in China. Through a meta-analysis of 108 studies and the application of a machine learning model, the yield effects of straw return were thoroughly examined. Nitrogen fertilizer inputs were identified having the most significant impact on yield, and the yield benefits of straw return stabilized after approximately 13 years. A optimized strategy for straw return was developed for provinces in China, resulting in average yield increases of 13.9 % for maize, 12.2 % for wheat, and 14.0 % for rice. Implementing these locally adapted straw return strategies will contribute to the long-term development of sustainable agriculture in China.

Straw as an important sustainable agricultural resource and its interaction with nitrogen (N) fertiliser may affect soil carbon sink and food security. Here, machine learning based on meta-analysis was conducted to assess the effect of straw and N input on soil organic carbon (SOC) and crop yield by compiling worldwide site-specific studies and high-resolution databases. The results highlight that the effects of straw return depend on management, climate, and soil properties. Meta-analysis results revealed that returning 8000-11,000 kg ha(-1)straw can achieve greater benefits. Moreover, the model forecasts demonstrate that optimizing straw and N input could increase surface SOC storage by 12 % (20.4 Pg) and global crop yield by 19.7 % (308 Tg). According to the optimization model, SOC storage and crop yield could further increase by 12.9 % (22.8 Pg) and 15.7 % (236.9 Tg) respectively by 2041-2060. These insights underscore the importance of optimizing straw and N input for sustainable agriculture under climate change.

Recommended management practices (RMPs, e.g., manuring, no-tillage, crop residue return) can increase soil organic carbon (SOC), reduce greenhouse gas emissions, and maintain soil health in croplands. However, there is no consensus on how RMPs affect the SOC storage potential of cropland soils for climate change mitigation. Here, based on 2301 comparisons from 158 peer-reviewed papers, a meta-analysis was conducted to explore management-induced SOC stock changes and their variations under different conditions. The results show that SOC stocks in the 0-20 cm layer were increased by 31.8% when chemical fertilization combined with manure application was compared with no fertilizer; 9.98% when no-tillage was compared with plow tillage; and 10.84% when straw return was compared with removal. The RMPs favorably increased SOC stock in arid areas, and in alkaline and fine-textured soils. Initial SOC, carbon-nitrogen ratio, and experimental duration could also affect SOC storage. Compared with the initial SOC stock, RMPs increased the SOC sequestration potential by 2.6-4.5% in the 0-20 cm soil depth, indicating that these practices can help China achieve targets to increase SOC by 4.0%o. Hence, it is essential to implement RMPs for climate change mitigation and soil fertility improvement.

Enhancing soil organic carbon (SOC) sequestration and food supply are vital for human survival when facing climate change. Site-specific best management practices (BMPs) are being promoted for adoption globally as solutions. However, how SOC and crop yield are related to each other in responding to BMPs remains unknown. Here, path analysis based on meta-analysis and machine learning was conducted to identify the effects and potential mechanisms of how the relationship between SOC and crop yield responds to site-specific BMPs in China. The results showed that BMPs could significantly enhance SOC and maintain or increase crop yield. The maximum benefits in SOC (30.6%) and crop yield (79.8%) occurred in mineral fertilizer combined with organic inputs (MOF). Specifically, the optimal SOC and crop yield would be achieved when the areas were arid, soil pH was ≥7.3, initial SOC content was ≤10 g kg-1, duration was >10 years, and the nitrogen (N) input level was 100-200 kg ha-1. Further analysis revealed that the original SOC level and crop yield change showed an inverted V-shaped structure. The association between the changes in SOC and crop yield might be linked to the positive role of the nutrient-mediated effect. The results generally suggested that improving the SOC can strongly support better crop performance. Limitations in increasing crop yield still exist due to low original SOC levels, and in regions where the excessive N inputs, inappropriate tillage or organic input is inadequate and could be diminished by optimizing BMPs in harmony with site-specific conditions.

No-tillage (NT) has obvious advantages in reducing input and labour costs. However, some farmers have raised concerns about adapting continuous NT to manage farmland due to problems such as soil stratification and less yield. Therefore, occasionally targeted tillage (known as strategic tillage, ST) has been proposed as a flexible management measure. To evaluate the potential impact of a typical ST pattern on soil properties and yield, a 12-year positioning field trial was conducted with three tillage practices, including long-term no-tillage (NT), ploughing tillage (CT), and ST (3-year NT and 1-year CT), in an intensive double-cropped rice system in southern China. ST could alter soil physicochemical properties by reducing soil stratification and potentially increasing nutrient availability. ST alleviated the bulk density (BD) stratification caused by the continuous decrease in 0-5 cm BD and the continuous increase in 5-10 cm BD under NT, due to the periodic use of CT. Compared with NT and CT, ST increased the soil available K (AK) and available P (AP) concentrations without affecting the SOC or TN storage throughout the profile. However, ST lowered the soil acidification at the soil surface (0-5 cm) while increasing the risk of soil subsurface acidification. Relative to ST, yields with NT trended lower over time, and the yield gap between NT and ST increased as the experiment progressed. The multiyear average yield of ST was 0.31 t ha-1 higher than that of NT but lower than that of CT. ST had the potential to improve the low yield under NT. It may be related to the fact that the seed setting rate (the proportion of filled to total seeds) of ST was significantly higher than that of NT (p < 0.05). In conclusion, strategic tillage is a more sustainable tillage method than continuous no-tillage and ploughing tillage in double-cropped rice systems in southern China.

Conservation agriculture (CA) can be an important strategy for improving soil organic carbon (SOC) and total nitrogen (TN). Numerous studies have examined SOC and TN dynamics in different cropping systems. However, there is some uncertainty regarding the relative impacts of some CA practices, and it is not always clear how other agricultural management, particularly nitrogen addition, interacts with these practices to influence SOC and TN sequestration. Thus, we conducted a global meta-analysis of 752 comparisons from 97 papers to analyze the impacts of nitrogen fertilizers and CA practices (namely crop diversification, minimal soil disturbance (no-tillage) and permanent soil cover), on SOC and TN content worldwide. Overall, our study showed the most significant increase of SOC [21.39 % (CI = 15.16 to 28.64)] and TN [54.34 % (CI = 26.19 to 96.69)] stock with CA practices compared to conventional practices in the 0-15 cm soil depth. It also showed a significant increase in SOC and TN stock with all the individual components of CA compared to conventional practices in the 0-15 cm soil depth. However, the impact of CA on SOC and TN is reduced in 0-60 cm depths compared to surface soil depths due to the limited input of crop residue deeper in the soil profile. Manure and manure mixed with mineral-N led to greater SOC sequestration [20.67 % (CI = 15.23 to 27.10) and 41.67 % (CI = 31.03 to 52.79), respectively] than mineral-N alone [9.08 % (CI = 6.44 to 11.83)]. Cropping systems that included legume residue decreased the C/N ratio. This highlights that adequate mineral-N fertilizer addition may also be required in conjunction with residue retention practices to improve SOC and TN content. Overall, these results show that CA systems that include legume residue and manure mixed with mineral-N have great potential to increase SOC and TN, particularly at 0-15 cm and 0-30 cm soil depth.

Water shortage is a serious threat to agriculture production in the North China Plain. Sustainable management practices can improve the water use efficiency of winter wheat, but currently no academic consensus has been reached. Therefore, we performed a meta-analysis that included 2194 observations from 209 articles to assess the water use efficiency of wheat in this area. The groundwater provides for 34%–37% of wheat evapotranspiration, which increases the decline of groundwater levels. The management of wheat irrigation appears to be the key process in improving agricultural water use efficiency. We observed from regression analyses that the factors such as climate, soil, and management significantly affect the water use efficiency of wheat (p < 0.05). The data showed that nitrogen input and irrigation significantly increased wheat yields (p < 0.05), but irrigation did not significantly improve the water use efficiency compared to rain-fed wheat. The optimal water use efficiency was obtained when the irrigation amount was 80–160 mm, or irrigation was applied twice, or the seasonal irrigation amount plus precipitation was ≤ 240 mm. In contrast, a nitrogen input significantly increased evapotranspiration and water use efficiency. The water use efficiency improvement was especially prominent when the nitrogen application rate was 220–250 kg·ha−1. Moreover, subsoiling and straw return should be recommended for increasing yield, reducing evapotranspiration, and improving water use efficiency. These practices can ultimately save over 240 mm of water and 75 kg·ha−1 of nitrogen, which contributes to a sustainable agricultural development. Here, we demonstrate for the first time the impact of management practices on crop water use efficiency at a regional scale and propose a sustainable agricultural development scheme.

The carbon (C) and nitrogen (N) cycles play an important role in agro-ecosystems. The interaction of both elements is a complex process, i.e., high soil organic carbon (SOC) and low N levels affect soil microbial biology and nutrient balance which can be improved through input of N. Therefore, an increase in N favors SOC sequestration by improving microbial activities. Legume-based biological nitrogen fixation (BNF) contributes about 50-70Tg N ha(-1) globally, and strongly impacts SOC sequestration. However, research information about the process of SOC sequestration with an increase in N by legume cultivation is scant. This review highlights the principal mechanisms by which cultivation of legume can enhance soil fertility and functioning through interaction of N and SOC, and vice versa. Legume cultivation leads to a simultaneous increase in N and SOC through rhizodeposition and root senescence and decomposition. Legume cultivation can also improve SOC due to the increased microbial activity and subsequent soil structural improvement (aggregation) induced by the addition of organic residues with favorable C/N ratio. Legume inclusion significantly increased SOC sequestration potential than other cropping systems, and legume residue addition has higher decomposition rate than cereals that increase SOC addition rate. However, additional research is needed to understand the pertinent role of root exudates and associated microbes in sequestration of SOC and N. Synthesis of the available information indicates that legume cultivation is an important option to sequester SOC and N for sustainable food production and environmental restoration.

Inappropriate nitrogen (N) use in maize (Zea mays L.) production can reduce crop productivity, decrease farm profitability, and cause serious environmental pollution. However, there is no consensus among researchers on the most appropriate farming practices regarding N use. We conducted a meta-analysis based on 987 observations from 82 summer maize studies in the North China Plain (NCP). Our results suggested that the N use efficiency of summer maize was less than 28%. Compared with no treatment, the individual use of N input, irrigation, or straw return could significantly increase the partial factor productivity of applied N (PFPN) and the aboveground N uptake (P < 0.05). Further analysis revealed that the increase in PFPN with N input was enhanced when soil total N was > 1.01 g kg(-1), soil pH was <= 8.12, and bulk density was < 1.35 g cm(-3). Particularly when the N application rate was in the range of 146-180 kg ha(-1), maize could achieve the best yield and PFPN. In addition, experimental duration, mean annual temperature, seasonal precipitation, irrigation amount, and irrigation times could also affect the PFPN. Based on this, appropriate farming practices with regulation N application rate at its core, using no-till and straw return to improve soil fertility, were recommended. Balancing the trade-off between yield and PFPN, our results suggested there was potential to decrease N use by 1.09-1.54 Mt yr(-1) in maize production in NCP, with associated environmental benefits.

Improving soil structural stability (SSS) and soil organic carbon (SOC) are critical for soil health and environmental pollution mitigation. No-tillage alters many soil properties (e.g., SOC), however, its effects on SSS in rice paddies are unclear. Therefore, we used field experiment and meta-analysis to determine the effects of no-tillage on wet stability of aggregates (WSA), clay dispersibility (ClayDis), mean weight diameter (MWD), and aggregate SOC distribution and mineralization in rice paddies. The field experiment included four tillage practices: no-tillage, rotary tillage and moldboard plow tillage with rice straw retention (NTS, RTS and CTS respectively), and moldboard plow tillage with rice straw removal (CT). The WSA at 0–5 cm soil depth was significantly higher under NTS compared with CTS. The ClayDis at 5–10 cm soil depth under NTS was 36% lower (P < 0.05) than CTS. The relationship between SOC and WSA fits a broken stick model, with an inflection point of clay/SOC ratio at 12.5. Higher SOC under no-tillage might result from the protection of >2 mm aggregates (macroaggregates) and lower SOC mineralization of < 2 mm aggregates. Additionally, the meta-analysis showed that no-tillage increased (P < 0.05) the macroaggregate content, WSA and MWD. However, the current research regarding tillage effects on paddy ClayDis is insufficient. In rice paddies, the increased macroaggregate content may contribute to increasing SOC, which improves SSS under no-tillage.